A Network Computing Scenario is one in which there are one or more boot servers with many network computers on the same network. These network computers load their operating systems with boot images present on these boot servers. These network computers depend on the Dynamic Host Configuration Protocol (DHCP) server which gives them their Internet Protocol (IP) addresses along with certain other parameters like the boot file server address, etc. which US enable them to boot up from the network.
Basic functionality of the DHCP/PXE proxy server is explained in FIG. 1 of the accompanying drawings wherein a network computing environment with two Pre Boot Execution Environment (PXE) clients and two boot servers and one DHCP/PXE proxy server has been shown. The working of the DHCP/PXE server is as follows:    1. When a PXE client seeks boot service from the network, it sends a DHCP discover packet to part (67) containing the PXE client extension tags    2. The DHCP server sends an extended DHCP offer packet to port (68) containing PXE server extension tags and other DHCP options tags including the client EP address    3. The PXE client then sends a request for installation to DHCP server port (67) containing PXE clients extension tags along with other DHCP option tags    4. The DHCP server sends the DHCP ACKnowledge reply to port (68)    5. The PXE client sends a boot server discover packet on the network to port (67) or (4011) of the allocated boot server containing the PXE client extension tags    6. The allocated boot server sends a boot server ACKnowledge reply on the network to the client source port containing PXE server extension tags    7. The PXE client sends a request for download of the network boot strap program to Trivial File Transfer Protocol (TFTP) port (69) of Multi Cast File Transfer Protocol (MTFTP) port.    8. The boot server downloads the network boot strap program (boot image) to the client port.
It may thus be seen that in this network, when a PXE client requests for IP address from DHCP server, it receives a DHCP offer packet, which contains the lists of the types and IP addresses of boot servers available on the network. The DHCP offer packet format is as follows:
Field LengthValueCommentOp(1)2Code for BOOTREPLYHtype(1)*Hlen(1)*Hops(1)*Xid(4)*Secs(2)*Flags(2)*Ciaddr(4)0.0.0.0Server Always sets thisvalue to ZeroYiaddr(4)a0,a1,a2,a3Client's IP Addressprovided by the serverSiaddr(4)a0,a1,a2,a3Next BootStrap ServerIP addressGiaddr(4)*Chaddr(16)*Client's MAC addressSname(64)*Can be overloadedusing option 66Bootfile(128)*can be overloadedusing option 6799.130.83.99DHCPOPTIONSTag NameTag NumberLengthData FieldDHCP Message5312 = DHCPOFFERTypeSERVER544A1,a2,a3,a4IDENTIFIERClient Machine9717TYPE(1) UUIDIdentifier(16)0 = UUIDClass Identifier609“PXEClient”Vendor Options43VariesEncapsulatedoptionsPXE DISCOVERY61CONTROLDISCOVERY_MC74Multicast IPAST_ADDRESSaddressPXE BOOT8VariesBoot ServerSERVERStype(2), Ipcnt(2),IP-addr-list(IPCnt *4), Boot Servertype(2),. . .PXE BOOT MENU9VariesBoot Servertype(2),desclen(1),“description”, Boot servertype(2). . .PXE MENU10VariesTimeout(1),PROMPTprompt
The PXE BOOT SERVERS tag contains the list of boot server addresses for each type of boot server and is made available to the PXE client.
The PXE client user via manual intervention i.e. by pressing the <F8> key after boot up would be able to select from the various types of boot servers that would be present on the network. The type of the boot server is indicated by the boot server type (2) field of the option.
However, this intervention by the user results in the selection of the boot server, which appears first in the list of DHCP offer packet. This normally results in overloading of the allocated boot server resulting in slow response to the PXE client.